Process of surface saponifying cellulose-2 1/2-acetate,and fabric made therefrom

ABSTRACT

CELLULOSE-2 1/2-ACETATE TEXTILE OR KNITTED FABRICS ARE MADE BY WETTING THE RAW MATERIALS; TREATING THEM AT ROOM TEMPERATURE AT A BATH RATIO OF BETWEEN 1:3 TO 1:10 IN A LYE SOLUTION WITH SLOWLY RINSING ALKALI CONENT WHICH IS FIRST RAISED UP TO ONLY 2% OF THE MATERIAL WEIGHT INTRODUCED. THE LYE SOLUTION IS THEN HEATED TO 80-100*C.; TREATING THE PRODUCT AGAIN IN A LYE SOLUTION WITH THE ALKALI CONTENT BEING SLOWLY INCREASED TO 4-5% OF THE INTRODUCED RAW MATERIAL WEIGHT, SO THAT THE SAPONIFICATION IS ONLY ON THE SURFACE.

United States Patent O Int. Cl. D06m 1/06 US. Cl. 8-130 4 Claims ABSTRACT OF THE DISCLOSURE Cellulose-2 /2-acetate textile or knitted fabrics are made by wetting the raw materials; treating them at room temperature at a bath ratio of between 1:3 to 1:10 in a lye solution with slowly rising alkali content which is first raised up to only 2% of the material weight introduced. the lye solution is then heated to 80-l00 C.; treating the product again in a lye solution with the alkali content being slowly increased to 45% of the introduced raw material weight, so that the saponification is only on the surface.

BACKGROUND OF INVENTION Present textile or knitted fabrics of cellulose-Z-Mz-acetate have several properties which are unsatisfactory to the processor or other user.

Because of the relatively low melting point of acetate for example, the ironability of a cellulose-2 /2-acetate is limited and can be carried out satisfactorily only at temperatures below 160 0., since the material to be ironed becomes rippled at higher temperatures. Present textile or knitted fabrics of cellulose-2 /z-acetate also have a low wash stability and a high electrostatic charge. Moreover dyed pieces have poor gas fading properties in using critical dyestuffs.

Similar disadvantageous properties are found in cellulose-triacetate. With cellulose triacetate, however, it was possible by means of surface saponification (S-finish) to improve these properties. This led to unsuccessful attempts to proceed similarly with respect to cellulose-2%.- acetate. The only success with these attempts was when the products were saponified to a very high degree so that the fiber consisted extensively of saponified cellulose and still contained only an insignificant nucleus of cellulose- 2 /2-acetate. This resulting fiber, however, no longer had the properties of a cellulose-acetate fiber. Furthermore, it acted as a viscous fiber; it could no longer be dyed with acetate dyestuffs (dispersion dyestuffs) and had, because of the high saponification, a lowering in weight, since normally it is saponified up to acetyl numbers of about 40.

Up to the present time it has not been possible to produce a cellulose-2 /2-acetate where only a surface saponification had been undertaken. This is due ot the considerably lower alkali stability of the cellulose-2 /2-acetate, as compared with triacetate. In technical particle sizes, this low alkali stability always led to different saponification grades, so that under operating requirements in the subsequent dyeing process, dye inequalities always resulted which made the product thus treated, unsalable. A surface-saponified 2 /2-acetate fiber per se is desirable, since compared to the intensely saponified acetate fiber it does not have or has only to a slight degree the undesirable properties described above.

SUMMARY OF INVENTION A process for the surface saponification of cellulose- 2 /2 -acetate which avoids these dlsadvantages is the ob ect of the present invention.

3,595,605 Patented July 27, 1971 In accordance with this invention the wetted product running without tension on a jig first passes throughat room temperaturea lye solution bath which is brought to lye content from l2% referring to the product weight, at a bath ratio to the product introduced of 1:3 to 1:10 by product weight. The bath is then heated to l00 C., preferably -90" C. (since at a higher temperature unpleasant handle influencing results). Several product passes are then carried out, the proportion of the lye solution being increased to 3, then 45% (with respect to the product weight). The operation life of the product in this bath amounts to about 1 hour. The lye solution is discharged. The product is washed and subsequently neutralized with acetic acid. Then it is finished in the usual, unclaimed process. The thus obtained product has a uniform surface saponification which yields entirely even dye qualities. The acetyl number decreases at about 1.5- 2% in the above described treatment. This low surface saponification is sufiicient to greatly increase the ironability and wash stability. At the same time the electrostatic charge of this product is reduced to a fraction. The exhaust gas effectiveness is also considerably improved as compared to pieces not pretreated in such manner, particularly for critical dyestuffs.

DETAILED DESCRIPTION The above-described process is amplified by the following example which, of course, does not limit the claimed invention in any manner.

EXAMPLE 1200 m. lining of cellulose-2 /2-acetate, raw material width 143 cm., square meter weight about g., acetyl number 54.8%, are placed on a low-tension fast running jigger, e.g. Poensgen system, with a running tension of 4-5 kg. The material is wetted in water in two passes at 25-30 C.', the wetting bath is then discharged. At a ratio of bath to the product introduced of 1:5 by product weight a bath is prepared of 2.5 gr./l. of alkali-containing washing agent and 1% (referring to the product weight) of potassium hydroxide. The product passes through the bath once at 22 C. By dissolving new potassium hydroxide, the alkali content of the bath is doubled. A second product pass takes place. The bath is then quickly heated to 87 C. while the goods are stationary. Two passes follow. Sufficient potassium hydroxide is then added so that the alkali content is 3%, referring to the product Weight. A new product pass follows; then the alkali content is again increased, so that it is finally 4%, referring to the product weight. At this alkali content, the product runs through the heated lye bath for 1 hour. The alkali solution is then discharged. Then washing takes place in cold water. Subsequently, it is neutralized in cold water acetate, then rewashed with water. Thereafter it is dyed and finished in the customary manner. The thus obtained product has an acetyl number of 52.8%, its ironability, without rippling, has been increased from to 233 C., the wash stability has been stepped up from 26,350 revolutions up to hole formation to 51,300 revolutions, and the electrostatic charge has been decreased from -1700 v./ cm. to 1000 v./cm.

What is claimed is:

1. A process for obtaining cellulose-Z-Vz-acetate fabric of improved ironability, increased wash stability and decreased electrostatic charge, characterized in that after wetting with water in two passes at approximately room temperature, the raw materials are first treated in a solution of potassium hydroxide at room temperature and a bath ratio between 1:3 to 1:10 with slowly rising alkali content which is first raised from passage to passage in the jig of only 1% to about 2% of the material weight introduced, heating the solution to 80-100 0, treating the product in the heated solution for about one 4-5% of the introduced raw material weight in steps of 1% and thereby limiting the saponification to the surface.

2. A process as set forth in claim 1 wherein the lye solution is heated to 85-90 C.

3. A process as set forth in claim 1 wherein the resultant fabric has a decreased acetyl number in its surface area, ironability Without rippling at about 200 C., wash stability without hole formation at about 50,000 revoluhour with the alkali content being slowly increased to 5 4 tions, and and electrostatic charge of about 1000 volt/ 4. A fabric made by the process of claim 1.

References Cited UNITED STATES PATENTS 1,897,691 2/1933 Dreyfus et al 8-130X GEORGE F. LESMES, Primary Examiner I. R. MILLER, Assistant Examiner U.S. CL. X.R. 

